The present invention relates to a brushless motor for use in a vehicle, etc., and, particularly, to an improvement of a total construction thereof.
FIG. 2 is a cross section of a conventional brushless motor which comprises a stator core 1, a stator coil 2 wound on the stator core, a rotor 3 having a shaft 4 on which a rotor core 5 and a main magnet 6 are coaxially fixedly mounted and further a submagnet 7 is also fixedly mounted on the shaft 4.
A rear bracket 8 has an opening fitted on a step portion a formed on an outer periphery of the stator core 1. A front bracket 9 has an opening fitted on a step portion b formed on the other outer peripheral edge of the stator core 1. The stator core 1, the rear bracket 8 and the front bracket 9 are assembled all together by through-bolts 10, the number of which is usually 3 to 4.
A rear bearing 11 is supported by the rear bracket 8 and a front bearing 12 is supported by the front bracket 9. The bearings 11 and 12 support opposite end portions of the shaft 4 rotatably.
A Hall element 13 is supported by a holder plate 14 fixed by screws to an inner wall of the rear bracket 8. The Hall element is positioned in opposing relation to the submagnet 7 for detecting the rotational position of the rotor 3, upon which the direction of current supplied from a drive circuit which is not shown to the stator coil 2 is switched sequentially to thereby obtain a continuous rotation of the rotor.
As shown, the submagnet 7 and the Hall element 13 are arranged within a space provided on the rear side. This is because a large space can be provided in this portion since the size of the rear bearing 11 on the end opposite to the output end is usually smaller than that of the front bearing 12.
Since the conventional brushless motor is constructed as mentioned above in which there are the fitting step portions a and b provided on the outer peripheral edges of the stator core 1 for the rear bracket 8 and the front bracket 9, respectively, there is a tendency of water invasion through the fitting portions into the motor and through gaps around the through-bolts 10 when the motor is used for a vehicle. Therefore, it is necessary to provide packings for these portions or a cover for covering the whole motor, which makes the construction complicated and the size larger.